The present invention relates to a supporting joint of the kind having a casing and a ball pin and ball held in the casing by a support comprising, on the ball pin side, a shell-shaped receptacle, oppositely to the ball pin a pressure shell having a cutout in a central support region thereof, and on a rear side relative to the pressure shell a cover supporting the pressure shell and having a curved support surface corresponding substantially to a curvature of the ball.
Supporting joints are known and can, for example, be installed in double wishbone axles having spring-loaded lower transverse links. Because of tire contact load, forces acting at right angles to the road surface are produced in such arrangements and, for example, subject the supporting joint to tensile loads.
Because such loads, i.e. the aforementioned tensile forces, are not always equal in magnitude, devices which compensate for the resulting play must be provided in the supporting joint interior. The play compensation component used is usually one of a deformable material, generally a plastic. This component, which can be configured as a pressure shell, lies against the supporting joint cover, against which it is pressed by the ball of the supporting joint, and also lies against the casing wall of the supporting joint. Because of this two point contact, that is, viewed spatially, on two annular surfaces, the pressure shell can deform only very slightly or not at all to compensate for play. Thus, either the play compensation is inadequate or the supporting joint can be moved only with great difficulty because the pressure shell has dimensions such that very high frictional moments occur between the pressure shell and the ball of the supporting joint.
Furthermore, the play compensation component, namely the pressure shell, adapts itself to the shape of the casing cover. This process takes place in particular on the outer periphery of the pressure shell. Hence, when the supporting-joint casing is rolled-in, the pressure shell presses against the ball over a large radius. The frictional moment of the joint or the frictional moment tolerance is thereby negatively influenced.
When the cover is pressed in, a wedging action additionally occurs in the region between the pressure shell and the ball. In the additional event of pressure loading, an axial softness or elasticity can still occur between the ball and the casing or the support because, in the inner region with a smaller radius, a clearance exists between the cover and the pressure shell. Axial softness in the joint is, however, impermissible, because damage to the supporting joint must be verified through the absence of play.
In addition, no large fluctuations of frictional moment should occur in the supporting joint, so as to enable the latter to move with, as far as possible, defined friction.
In U.S. Pat. No. 3,401,962 a joint has a rotatable, partly spherical bearing pin. An intermediate plate lies on the bearing pin and, together with the bearing pin, can be turned relative to a bearing part or directly relative to a bearing part. The bearing part thus constitutes a stationary part relative to the rotatable bearing pin and, where applicable, also relative to the intermediate plate. To avoid direct contact between the bearing part and the bearing pin or the intermediate plate, and to ensure contact only through 0-rings, the radius of the bearing shell is larger than the radius of the bearing pin. The resulting radius serves as a contactless lubricant chamber.
An object of the present invention is to provide a supporting joint which has the greatest possible insensitivity to tolerances without requiring adjustment.
This object has been achieved in accordance with the present invention by providing that referred to an installed state of the supporting joint, the thickness of the pressure shell in the central support region, measured in an uninstalled state of the supporting joint, is greater than a distance between the ball and the support surface of the cover.
Through the selection of the pressure shell thickness, in accordance with the present invention, which thickness in the uninstalled state is greater than the distance between the ball and the support surface of the cover, it is ensured in a simple manner, by pressing the pressure shell, that on installation the joint is free from play and that the frictional moments of the joint or the frictional moment tolerances are not negatively influenced. Thus, the supporting joint can be moved with as far as possible defined friction. The pressure shell material displaced by the pressing can then escape into the central cutout.